WBS, Work Breakdown Structure

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This article examines the WBS, an acronym for Work Breakdown Structure. As a project manager it is important to possess certain competencies and qualities to achieve a successful project. However, personal skills such as communication, conflict management and being motivational are not sufficient on its own to make a project successful. As a project manager it is crucial to be aware and recognize the usefulness of various tools and concepts to help consider all aspects of a project, ranging from purpose, risks and planning. The Work Breakdown Structure is a common tool used in project management to establish an overview of the project at hand and to divide tasks into smaller and more manageable sections. This is a powerful concept when planning complex projects because it visualizes the scope of the project in a hierarchical way, and furthermore because it helps identify key process groups, such as Project Planning, Scheduling, Risk- and Resource Management, Team Management, etc. This article aims at providing an overall understanding of the WBS, including its purpose, different types, various levels and specific elements. Constructing a detailed WBS is essential to create the best project overview, however, it is equally crucial to go just deep enough, so that the WBS does not get confusing. Hence, a WBS must be simple but not simplistic. If not simple the WBS loses its relevance and usefulness to the project manager. If simplistic, then the project manager risks missing something crucial. Examples of a Work Breakdown Structure and illustrations are included to emphasize the theory and solidify its purpose. Finally, the advantages and disadvantages of the Work Breakdown Structure are presented to clarify the strengths and weaknesses of using this tool.


“The art of simplicity is a puzzle of complexity” (Douglas Horton).[1] A puzzle consists of many small pieces that together create art. Likewise, a project also consists of many small tasks executed by many different people. Separating the project into smaller pieces of doable tasks makes it possible to delegate. Coordinating these smaller tasks, so that they together contribute to the purpose of the project, as the small puzzle pieces fit together, makes every piece integrated.

Work Breakdown Structure

A Work Breakdown Structure is an efficient tool used in Project Management to simply break the work down into various subsections that create a structured approach to the project.[2] A WBS is a product-oriented family tree that identifies the deliverables required to achieve the project end. In the PMBOK the Work Breakdown Structure is defined as "The WBS is a hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverables. The WBS organizes and defines the total scope of the project and represents the work specified in the current approved project scope statement." [3] The Work Breakdown Structure is a hierarchical and visualized approach to divide the work into several substantial chunks, which further breaks down into new more detailed chunks where each descending level represents an increasingly detailed definition of the project work. This decomposition creates an overview of the tasks needed to accomplish the project and makes it more manageable. The WBS is a powerful tool to use in the planning phase to help kickstart the project and to visualize how the project can evolve. It further enables increased tracking in later stages of the project as specific tasks are completed.

WBS elements

There are some key components which a typical Work Breakdown Structure consists of. These components are listed below and are accompanied by a brief introduction to some of the terms subsequently used in this article. [4]

WBS Dictionary To navigate in a complex project, it is important to have a WBS dictionary that defines the elements in the project work. This is a supplement to the visual tool the WBS provides and gives more detailed information about the activities in order to keep the WBS simple and with information held at a minimum. This helps accomplish the hurdle of “simple but not simplistic”. Often the substantial chunks in the Work Breakdown Structure have a title and a number that refers to the WBS Dictionary. [5]

WBS Levels The levels are an essential factor to create the hierarchical structure that makes the WBS efficient. It is important not to have too many levels in the WBS because it can cause a messy and complicated structure, which is the opposite of the main purpose of the tool - which is to make a simple and visual structure of a complex project. The most common Work Breakdown Structures have three levels, which consist of (i) the project’s main deliverables, (ii) the project’s deliverables and (iii) the work packages. [6]

Project Deliverables Project deliverables are not the final outputs of the project but the outcome of the work packages. It refers to the all the outputs that are submitted within the scope of the project. The project deliverables are those defined in level 2 of the WBS.

Work Packages The work packages are the lowest level of the WBS. It is a group of tasks that seems like a project themselves and can therefore be assigned to a team member. These work packages help to get the tasks executed and contributes to the overarching goal of the final project. The work packages can vary in the level of detail due to the complexity and size of the project. However, the work packages must follow the “8 to 80” rule which indicates that the work should take more than 8 hours but less than 80 hours. [7] The work packages also contribute to an estimation of costs and durations of the project.

Defining the Work Breakdown Structure

As mentioned before in "WBS elements - Project Deliverables section" the most common Work Breakdown Structure has a least three levels. Figure 1 shows a simple WBS with 3 levels, where the final deliverable is defined in Level 1. Level 2 visualizes the main deliverables and Level 3 can be the deliverables to the customer. Hereafter the Work Packages has been defined and can be assigned to a team member.

Figure 1: Illustration of the Bottom-Up approach. Made with inspiration from [8]

This visual insight in the project makes it possible to create a rough estimate of the time schedule and the budget, which can be a huge advantage for the project manager. Furthermore, the WBS can clarify which skills are needed to complete the final project and if there needs to be hired more experts to accomplish the project. The benefits of using a WBS early in the planning phase is wide ranging. Below is highlighted the main benefits of using a WBS.

  • The main benefit of the WBS is that it gives a clear and visual understanding of the scope for both the project leader, the team members and the stakeholders. A clear vision also contributes to a general understanding of the expectations throughout the team. Furthermore, a clear scope should also relieve the project manager from some workload because it shortens the process and the team members are aware of their specific tasks.
  • The deliverables get more manageable for the team members by simplifying the work.
  • It is a great method to start regionalizing other processes within the project management like risk analysis, budgeting and scheduling.


How to develop a WBS

First it is important to realize that developing a WBS is a team task. This is because each member of the team might have some knowledge about the requirements to the deliverables. It is crucial to have enough information about the deliverables so there won’t occur any surprises when the project starts. However, it is also important that the WBS is not too rigid so that no flexibility exists, as small changes may be necessary as the project progresses and new information is uncovered. As mentioned, a detailed WBS also contributes to a well-organized time schedule because of the awareness of the needed tasks and budget. The most typical way to develop a Work Breakdown Structure is by using the ‘Top-Down’ or ‘Bottom-Up’ approaches.

Top-Down approach

As the name indicates this method is about creating a Work Breakdown Structure from top to bottom. This means that you start with the project goal and then step by step divides it into more manageable tasks. This process of breaking down tasks into subtasks can be continued until you can assign the tasks to a team member. It is an advantage to use this Top-Down approach if there is a clear goal to reach and to clarify which tasks need to be accomplished to reach this goal.

Bottom-Up approach

This method is about creating a WBS from the bottom to the top. This approach begins with brainstorming solutions to reach the final project goal. This means that the final deliverable is known, but the road to it is not clear yet. This approach is very good to use when developing new products, where there is lack of prior experience. The approach makes it possible to brainstorm new solutions by identifying tasks and risks. As a result, the process is more creative, and every team member has a role in the decision-making process.

Figure 2: Illustration of the Bottom-Up approach. Made with inspiration from [9]

100% Rule

To create a successful Work Break Structure, it is crucial to follow the 100% rule. The 100% rule represents 100% of the work which is needed to fulfill the project. Therefore, it is important that each level within the WBS hierarchy must sum to 100% of the work needed to complete the outcome in the previous level.

Work Break Down Structure example

An illustration of a Work Breakdown structure is shown in figure 3. The figure shows a WBS of a new jewelry collection with the different levels and work packages. The chunks have a title and a number that refers to the WBS Dictionary mentioned earlier which makes it possible to keep the WBS simple and with minimal information. It is important to notice that the WBS don’t have to be symmetric within the decomposition. Furthermore, the WBS shows an example of how the 100% rule works by including 100% of the work defined by the project scope.

Figure 3: Illustration of a WBS. Made with inspiration from [10]


Despite the many benefits a WBS contributes to, such as making a complex project more manageable, creating an overview of the task and the budget, a WBS also has its limitations. It is important to be aware that a WBS is not a schedule or budget and can only give an estimation of these factors. As a result, the WBS must be supported by a Gantt Chart for further scheduling. Moreover, because of the simple structure, deliverables with similarity might be combined into the same chunk even though they require different tasks. This simple structure with minimal information may cause some details to be left out. As the project evolves it is crucial to keep the WBS updated. If not, the WBS won’t visualize the correct deliverables and it therefore risks being outdated as new insights are uncovered.

Furthermore, there can be some limitations with regards to using either the Top-Down or Bottom-up approach when creating the WBS.

The Top-Down approach minimizes the creativity in the project, because each team member has been delegated their own responsibilities and becomes unable to influence the overall process. This might also result in slow decision-making when an unexpected challenge occurs, because there are limited minds participating in the decisions. [11]

The Bottom-Up approach has opposite limitations as the brainstorming can lead to delays in creating a project plan and reaching the final goal. The huge influence from all team members can also lead to conflicts in the decision-making, because everybody has an idea of how the project should unroll. [12]

Annotated bibliography

  • Project Management Institute Inc.(2017) "A Guide to the Project Management Body of Knowledge (PMBOOK)" 6th edition)

This book has been used to collect information about WBS and project management i generel. PMI has developed this guide as a standard, which has contains tools and principles used in project management.


  1. https://www.brainyquote.com/quotes/douglas_horton_152740
  2. https://www.workbreakdownstructure.com/
  3. Project management institute inc.(2017) "A Guide to the Project Management Body of Knowledge (PMBOOK)" 6th edition)
  4. https://project-management.com/work-breakdown-structure-wbs/
  5. https://www.workbreakdownstructure.com/wbs-dictionary
  6. https://project-management.com/work-breakdown-structure-wbs/
  7. https://project-management.com/work-breakdown-structure-wbs/
  8. https://gabriel-rabhi-dev.com/2019/02/14/les-richesses-cachees-des-notions-top-down-et-bottom-up-partie-1-fr/
  9. https://gabriel-rabhi-dev.com/2019/02/14/les-richesses-cachees-des-notions-top-down-et-bottom-up-partie-1-fr/
  10. https://projectinsight.com/project-management-basics/project-management-schedule
  11. https://www.smartsheet.com/top-down-bottom-up-approach
  12. https://www.smartsheet.com/top-down-bottom-up-approach
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